Electric arc detection device, switchgear unit comprising one such device and method for detecting an electric arc

Abstract

The invention relates to an electric arc detection device comprising analyzing means supplying current and voltage integration signals. The analyzing means supply current and voltage differential signals. Decision-making means comprise a disable unit supplying adaptive disable signals and comprising detection means supplying at least one decision-making aid signal according to at least one adaptive disable signal and to the current differential signal or the current integration signal. A decision-making unit supplies a trip signal according to the decision-making aid signals.

1. Electric arc detection device comprising
 measuring means for measuring an AC current and an AC voltage, 
 analyzing means connected to the measuring means, and comprising
 computing means for computing, at the rhythm of a sequencing signal, an integral of an absolute value:
 of the AC current over at least one mains half-wave and supplying a current integration signal, 
 of the AC voltage over at least one mains half-wave and supplying a voltage integration signal, 
 
 differentiation means supplying
 a current differential signal representative of the difference between a first current integration signal and a second current integration signal measured over a period before said first integration signal, 
 a voltage differential signal representative of the difference between a first voltage integration signal and a second voltage integration signal measured over a period before said first integration signal, 
 
 
 decision-making means connected to the analyzing means and designed to send at least one trip signal, 
 
     wherein the decision-making means comprise:
   a disable unit supplying adaptive disable signals,   detection means each designed to supply at least one decision-making aid signal according to:
 at least one adaptive disable signal, and 
 the current differential signal or the current integration signal, 
   a decision-making unit designed to supply at least one trip signal according to the value of decision-making aid signals.   
 
   
   
     2. Detection device according to  claim 1 , comprising a synchronization unit synchronizing the sequencing signal with zero crossing of the AC voltage. 
   
   
     3. Detection device according to  claim 2 , wherein the disable unit supplies a first active adaptive disable signal when the sequencing signal is no longer synchronized on zero crossing of the AC voltage. 
   
   
     4. Detection device according to  claim 1 , wherein the disable unit supplies a second active adaptive disable signal when the current differential signal follows the same variation as the voltage differential signal throughout the duration of a current analysis period. 
   
   
     5. Detection device according to  claim 1 , wherein the disable unit supplies a third active adaptive disable signal when the current differential signal decreases to a zero value after undergoing a sharp increase. 
   
   
     6. Detection device according to  claim 1 , wherein the disable unit supplies a fourth active adaptive disable signal when the AC current is of asymmetric shape with respect to zero current line, the asymmetric tending to decrease and then cancel out. 
   
   
     7. Detection device according to  claim 1 , wherein the disable unit supplies a fifth active adaptive disable signal when a decrease of the current differential signal is greater than the means value of the current integration signal. 
   
   
     8. Detection device according to  claim 3 , wherein a first detection means designed to detect electric arcs of very strong intensity supplies a first decision-making aid signal if, over a first analysis period:
 the current integration signal is higher than a saturation threshold at least once, and 
 the first adaptive disable signal is inactive. 
 
   
   
     9. Detection device according to  claim 8 , wherein the first detection means comprise first storage means counting the number of times the current integration signal is higher than the saturation threshold. 
   
   
     10. Detection device according to  claim 9 , wherein the first detection means supply a first decision-making aid signal if the number of times the current integration signal is higher than the saturation threshold is greater than a first counting threshold. 
   
   
     11. Detection device according to  claim 8 , wherein the duration of the first analysis period is comprised between 0 and 0.2 seconds. 
   
   
     12. Detection device according to  claim 1 , wherein a second detection means designed to detect electric arcs of strong intensity supplies a second decision-making aid signal if, over a second analysis period:
 the current differential signal is successively:
 higher than an absolute threshold at least once, 
 increasing with a higher variation rate than a relative variation threshold, and 
 
 the first, second, third and fourth adaptive disable signals are inactive. 
 
   
   
     13. Detection device according to  claim 12 , wherein the second detection means comprise second storage means counting the number of times the current differential signal is successively higher than the absolute threshold, and is then increasing with a higher variation rate than a relative variation threshold. 
   
   
     14. Detection device according to  claim 13 , wherein the second detection means supply a second decision-making aid signal if the number of times the current differential signal is successively higher than the absolute threshold, and is then increasing with a higher variation rate than a relative variation threshold, is greater than a second counting threshold. 
   
   
     15. Detection device according to  claim 12 , wherein the duration of the second analysis period is comprised between 0 and 0.2 seconds. 
   
   
     16. Detection device according to  claim 1 , wherein a third detection means designed to detect saline arcs of medium intensity supplies a third decision-making aid signal if, over a third analysis period:
 the current differential signal is higher than a first saline threshold at least once, while at the same time not having been lower than a first series threshold during the previous two half-waves of the AC current, and 
 the first, second, third and fourth adaptive disable signals are inactive. 
 
   
   
     17. Detection device according to  claim 16 , wherein the third detection means comprise third storage means counting the number of times the current differential signal is higher than a first saline threshold, while at the same time not having been lower than a first series threshold during the previous two half-waves of the AC current. 
   
   
     18. Detection device according to  claim 17 , wherein the third detection means supply a third decision-making aid signal if the number of times the current differential signal is higher than a first saline threshold, while at the same time not having been lower than a first series threshold during the previous two half-waves of the AC current, is greater than a third counting threshold. 
   
   
     19. Detection device according to  claim 16 , wherein the duration of the third analysis period is comprised between 0 and 0.2 seconds. 
   
   
     20. Detection device according to  claim 1 , wherein a fourth detection means designed to detect series arcs occurring in a circuit with a large number of current interruptions supplies a fourth decision-making aid signal if, over a fourth analysis period:
 the current differential signal is lower than a first series threshold at least once, while at the same time not having been higher than a first saline threshold during the previous two half-waves of the AC current, and 
 the first, second, third and fourth adaptive disable signals are inactive. 
 
   
   
     21. Detection device according to  claim 20 , wherein the fourth detection means comprise fourth storage means counting the number of times the current differential signal is lower than the first series threshold, while at the same time not having been higher than the first saline threshold during the previous two half-waves of the AC current. 
   
   
     22. Detection device according to  claim 21 , wherein the fourth detection means supply a fourth decision-making aid signal if the number of times the current differential signal is lower than the first series threshold, while at the same time not having been higher than the first saline threshold during the previous two half-waves of the AC current, is greater than a fourth counting threshold. 
   
   
     23. Detection device according to  claim 20 , wherein the duration of the fourth analysis period is comprised between 0 and 0.2 seconds. 
   
   
     24. Detection device according to  claim 3 , wherein a fifth detection means designed to detect saline arcs of strong intensity supplies a fifth decision-making aid signal if, over a fifth analysis period:
 the current differential signal successively undergoes at least once:
 a first very sharp increase where said signal is higher than a second saline threshold, 
 a second increase that is less sharp than the first increase where said signal is lower than a third saline threshold, 
 a sharp decrease where said signal is lower than a fourth saline threshold, 
 
 the second saline threshold being higher than or equal to the third saline threshold and the third saline threshold being higher than the fourth saline threshold, and 
 the first adaptive disable signal being inactive. 
 
   
   
     25. Detection device according to  claim 24 , wherein the fifth detection means comprise fifth storage means counting the number of times the current differential signal successively undergoes a first very sharp increase, where said signal is higher than a second saline threshold, a second less sharp increase where said signal is lower than a third saline threshold, and a sharp decrease where said signal is lower than a fourth saline threshold. 
   
   
     26. Detection device according to  claim 25 , wherein the fifth detection means supply a fifth decision-making aid signal if the number of times the current differential signal successively undergoes a first very sharp increase, where said signal is higher than a second saline threshold, a second less sharp increase where said signal is lower than a third saline threshold, and a sharp decrease where said signal is lower than a fourth saline threshold, is greater than a fifth counting threshold. 
   
   
     27. Detection device according to  claim 24 , wherein the duration of the fifth analysis period is comprised between eight and twelve seconds. 
   
   
     28. Detection device according to  claim 3 , wherein a sixth detection means designed to detect series arcs occurring in a circuit with few current interruptions supplies a sixth decision-making aid signal if, over a sixth analysis period,
 the current differential signal successively undergoes at least once:
 a first very sharp decrease where said signal is lower than a second series threshold, 
 a second decrease that is less sharp than the first decrease, where said signal is higher than a third series threshold, 
 a sharp increase where said signal is higher than a fourth series threshold, 
 
 the second series threshold being lower than or equal to the third series threshold and the third series threshold being lower than the fourth series threshold, and 
 the first and fifth adaptive disable signals are inactive. 
 
   
   
     29. Detection device according to  claim 28 , wherein the sixth detection means comprise sixth storage means counting the number of times the current differential signal successively undergoes a first very sharp decrease where said signal is lower than a second series threshold, a second less sharp decrease where said signal is higher than a third series threshold, and a sharp increase where said signal is higher than a fourth series threshold. 
   
   
     30. Detection device according to  claim 29 , wherein the sixth detection means supply a sixth decision-making aid signal if the number of times the current differential signal successively undergoes a first very sharp decrease where said signal is lower than a second series threshold, a second less sharp decrease where said signal is higher than a third series threshold, and a sharp increase where said signal is higher than a fourth series threshold, is greater than a sixth counting threshold. 
   
   
     31. Detection device according to  claim 28 , wherein the duration of the sixth analysis period is comprised between a half a second and a second and a half. 
   
   
     32. Detection device according to  claim 1 , wherein analyzing means comprise a means for determining the maximum value of the AC current, at the rhythm of a sequencing signal. 
   
   
     33. Detection device according to  claim 1 , comprising means for sampling the measured current and voltage signals and comprises means for storing said sampled signals. 
   
   
     34. Detection device according to  claim 1 , comprising means for sampling the current and voltage integration signals and comprises means for storing said sampled signals. 
   
   
     35. Detection device according to  claim 1 , wherein the synchronization unit supplies a sequencing signal to the analyzing means synchronizing operation of each means for computing the current and voltage integration and differential signals on that of said sequencing signal. 
   
   
     36. Detection device according to  claim 1 , wherein the synchronization unit supplies a sequencing signal to each detection means synchronizing their operation with that of said sequencing signal. 
   
   
     37. Switchgear device comprising an opening mechanism of electric contacts and a control relay connected to a detection device according to  claim 1 , wherein the control relay is destined to receive at least one trip signal from the decision-making means of the detection device. 
   
   
     38. Method for detecting an electric arc comprising:
 measurement of an AC current and an AC voltage with measuring means, 
 computation at the rhythm of a sequencing signal,
 of an integral of an absolute value of the AC current and of the AC voltage over at least one mains half-wave, 
 of a current integration signal and a voltage integration signal, 
 
 supply of a current differential signal representative of the difference between a first current integration signal and a second current integration signal measured over a period before said first integration signal, 
 supply of a voltage differential signal representative of the difference between a first voltage integration signal and a second voltage integration signal measured over a period before said first integration signal, 
 
     comprising supply of a trip signal dependent on the value of decision-making aid signals, each decision-making aid signal being determined according to:
   supply of at least one adaptive disable signal and   the current differential signal or the current integration signal.   
 
   
   
     39. Method for detecting an electric arc according to  claim 38 , wherein it synchronizes the sequencing signal with zero crossing of the AC voltage. 
   
   
     40. Method for detecting an electric arc according to  claim 38 , comprising supply of a first active adaptive disable signal when the sequencing signal is no longer synchronized on zero crossing of the AC voltage. 
   
   
     41. Method for detecting an electric arc according to  claim 38 , comprising supply of a second active adaptive disable signal when the current differential signal follows the same variation as the voltage differential signal during an analysis period of the current. 
   
   
     42. Method for detecting an electric arc according to  claim 38 , comprising supply of a third active adaptive disable signal when the current differential signal decreases to a zero value after undergoing a sharp increase. 
   
   
     43. Method for detecting an electric arc according to  claim 38 , comprising supply of a fourth active adaptive disable signal when the AC current is of asymmetric shape with respect to a zero current line, the asymmetric tending to decrease and then cancel out. 
   
   
     44. Method for detecting an electric arc according to  claim 38 , comprising supply of a fifth active adaptive disable signal when a decrease of the current differential signal is greater than the mean value of the current integration signal. 
   
   
     45. Method for detecting an electric arc according to  claim 38 , comprising supply of a first decision-making aid signal if, over a first analysis period:
 the current integration signal is higher than a saturation threshold at least once, and 
 the first adaptive disable signal is inactive. 
 
   
   
     46. Method for detecting an electric arc according to  claim 38 , comprising supply of a second decision-making aid signal if, over a second analysis period:
 the current differential signal is successively:
 higher than an absolute threshold at least once, 
 increasing with a higher variation rate than a relative variation threshold, and 
 
 the first, second, third and fourth adaptive disable signals are inactive. 
 
   
   
     47. Method for detecting an electric arc according to  claim 38 , comprising supply of a third decision-making aid signal if, over a third analysis period:
 the current differential signal is higher than a first saline threshold at least once, while at the same time not having been lower than a first series threshold during the previous two half-waves of the AC current, and 
 the first, second, third and fourth adaptive disable signals are inactive. 
 
   
   
     48. Method for detecting an electric arc according to  claim 38 , comprising supply of a fourth decision-making aid signal if, over a fourth analysis period:
 the current differential signal is lower than a first series threshold at least once, while at the same time not having been higher than a first saline threshold during the previous two half-waves of the AC current, and 
 the first, second, third and fourth adaptive disable signals are inactive. 
 
   
   
     49. Method for detecting an electric arc according to  claim 38 , comprising supply of a fifth decision-making aid signal if, over a fifth analysis period:
 the current differential signal successively undergoes at least once:
 a first very sharp increase where said signal is higher than a second saline threshold, 
 a second increase that is less sharp than the first increase where said signal is lower than a third saline threshold, 
 a sharp decrease where said signal is lower than a fourth saline threshold, 
 
 the second saline threshold being higher than or equal to the third saline threshold and the third saline threshold being higher than the fourth saline threshold, and 
 the first adaptive disable signal is inactive. 
 
   
   
     50. Method for detecting an electric arc according to  claim 38 , comprising supply of a sixth decision-making aid signal if, over a sixth analysis period,
 the current differential signal successively undergoes at least once:
 a first very sharp decrease where said signal is lower than a second series threshold, 
 a second decrease that is less sharp than the first decrease, where said signal is higher than a third series threshold, 
 a sharp increase where said signal is higher than a fourth series threshold, 
 
 the second series threshold being lower than or equal to the third series threshold and the third series threshold being lower than the fourth series threshold, and 
 the first and fifth adaptive disable signals are inactive.